CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

Parallelization efficiency..

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Display Modes
Old   January 1, 2000, 07:46
Default Parallelization efficiency..
Posts: n/a
Hi all,

I am doing explicit unstructured Finite Volume CFD on a 24 node message passing parallel computer. I am getting efficiencies of more than 100% (around 115%) when using 2 & 4 nodes.

The problem size is relatively small (< 7 MB per node) comapared to the available memory (30 MB per node). Can anyone attribute reasons towards this?. Also, the efficiency is always maximum when i'm using 4 nodes. I have run codes for 4 different levels of grid and 'am consistently getting the same numbers.

Note: eff = time on 1 proc / (n * time on n proc) time : time per iteration.
  Reply With Quote

Old   January 4, 2000, 12:20
Default Re: Parallelization efficiency..
Noel Rycroft
Posts: n/a
Efficiencies greater than 100% are quite common for codes which are well suited to parallelisation. (This is termed "super-linear speed-up"). The reason is supposedly to do with increases in the efficiency of the cache use (at least on distributed memory machines).

As the number of processors increases the efficiency will then decrease because of the extra message passing so you should expect a maximum at some point.

Hope this helps a little.
  Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
MPI Aborts when using reactingFoam with cyclic BC in parallelization jose_rodrig OpenFOAM 1 February 14, 2011 04:05
Efficiency, thrust/drag with regard to hovering quarkz Main CFD Forum 0 April 21, 2010 00:51
Droplet Collision Efficiency Calculation using DPM Virk FLUENT 0 January 22, 2010 10:37
Parelleling Efficiency kassiotis OpenFOAM 0 June 19, 2009 14:12
Efficiency for hovering flight? Zonexo Main CFD Forum 1 April 14, 2008 00:49

All times are GMT -4. The time now is 18:25.